High speed cutting of difficult-to-machine materials with cutting tools coated by Ti-B-C thermally stable films

为了改善难加工材料钛合金(Ti-6Al-4V)的刀具性能，对钛-硼-碳(Ti-B-C)薄膜进行了涂层处理。以碳化硼(B_4C)靶材和钛靶材为原料，采用直流磁控溅射方法制备了Ti-B-C薄膜。首先，在硅衬底上进行了沉积实验，以优化Ti-B-C涂层的工艺条件。在沉积过程中，钛的靶功率为O~200W，甲烷气体流量为0~80sccm，以了解薄膜中钛和碳含量对纳米压痕硬度、摩擦性能和涂层结合强度的影响。提高镀膜过程中钛的靶功率，可以有效地提高薄膜与基材的结合强度。在镀膜过程中引入CH4后，薄膜的摩擦系数大大降低。此外，这些薄膜还获得了良好的耐磨性。在优化的涂层条件下，在碳化钨刀具上制备了Ti-B-C薄膜，并用涂层刀具对钛合金进行了车削试验。Ti-B-C涂层改善了钛合金的切割性能。采用Ti-B-C涂层降低了前刀面的刀具磨损。与未涂覆刀具形成的切屑相比，在车削测试期间产生的切屑也是平滑的。即使在干切削条件下，Ti-B-C涂层也能改善工件表面粗糙度。

We attempt to improve the performance of cutting tools against titanium alloy (Ti-6A1-4V), which is one of the difficult-to-cut materials, by coating of titanium-boron-carbon (Ti-B-C) thin films. We have been prepared the Ti-B-C thin films by DC magnetron sputtering using boron carbide (B_4C) target and titanium target. At first, the deposition experiments were performed with silicon substrates for optimizing the Ti-B-C coating condition. The target power for Ti was varied from O to 200W and CH_4 gas flow rate from 0 to 80 sccm in the deposition process to understand the influences of titanium and carbon contents in the films on the nano-indentation hardness, the frictional properties and the adhesive strength of coatings. Increase of the target power for titanium in the coating process was effective for increasing the adhesive strength of the films onto the substrates. As CH4 introduction in the coating process, the friction coefficient of the films was drastically decreased. Moreover, those films obtained good wear resistant. At the optimized coating condition, the Ti-B-C films were produced on tungsten carbide cutting tools and turning tests were carried out against titanium alloy with the coated tools. The Ti-B-C coating provided improvements in cutting performance against titanium alloys. Tool wear on rake face was decreased by Ti-B-C coating. Chip produced during the turning tests was also smoothed as compared to that formed by the uncoated tool. Surface roughness of workpieces was improved by Ti-B-C coating even in dry cutting.